This invention relates to a method of fabricating a compound semiconductor device, and more particularly to a method of fabricating a compound semiconductor device composed of a plurality of epitaxial growth layers differing in composition and conductivity type by a single growth step.
As a compound semiconductor device having a plurality of epitaxial growth layers differing in composition, for example, a semiconductor laser with multi-wavelength is known.
The semiconductor laser with multi-wavelength has plural laser emitting parts differing in wavelength contained in one element, and it is widely disclosed, for example, in U.S. Pat. Nos. 4,318,059, 4,476,563, 4,577,207, 4,607,070, 4,627,065, etc. A common defect of these semiconductor lasers with multiwavelength was that active layers of plural laser must be grown separately, which increased the number of steps of grwoth.
It was accordingly proposed to fabricate a semiconductor laser for emitting light in plural wavelengths by one growth step, and it was applied on Feb. 13, 1986 as U.S. Ser. No. 829,090. FIG. 3 of this application unveils the method of forming an MQW type semiconductor laser with multi-wavelength in a single growth step. That is, after growth of MOW layer, part of it is illuminated with light, and in this illuminated area, the composition of the thin film layer (MQW layer) is varied by thermal mechanism at the boundary of plural thin film layers which compose the MQW structure, so that the emission wavelength is different between the illuminated region and non-illuminated region of the MQW layer.
In this method, however, if applied to an ordinary semiconductor laser of double hetero junction type, it was not possible to obtain an effect equally comparable with that of the MQW layer.